Field of the Invention
The present invention relates to iron compound particles having a β-FeOOH crystal phase, a method for producing the iron compound particles, and an oxidation catalyst using the iron compound particles.
Related Background Art
As one solution to problems concerning global environment and fossil fuel depletion, attention has been focused on the utilization of hydrogen energy and carbon dioxide fixation technique. Above all, a water splitting reaction by which water is decomposed into hydrogen and oxygen at normal temperature and normal pressure and a reduction reaction of carbon dioxide using water as an electron source are expected as clean energy generation methods. These reactions inevitably require that water should undergo an oxidation reaction:2H2O→O2+4H++4e−, 1.23 V (vs. RHE)However, since the reaction efficiency is low, there have been demands for a catalyst which promotes the water oxidation reaction. As such water oxidation catalysts, oxides including cobalt oxide, ruthenium oxide, iridium oxide, and the like have been known conventionally.
In addition, recently, water oxidation catalysts utilizing an iron compound such as Fe2O3 or FeOOH have been reported, too. However, if an iron compound such as Fe2O3 or FeOOH is amorphous, this brings about a problem that the oxidation catalyst has a low activity in comparison with other oxide catalysts.
Hence, W. D. Chemelewski et al., J. Mater. Chem A, 2014, Iss. 2, pp. 14957 to 14962 (Non Patent Document 1) have proposed, as an oxidation catalyst, amorphous FeOOH doped with a Ni element. Although the Ni doping improves the catalytic activity, this oxidation catalyst does not always have a sufficiently high catalytic activity.
Further, A. E. Tufo et al., Hyperfine Interact, 2014, Vol. 224, pp. 239 to 250 (Non Patent Document 2) have proposed β-FeOOH doped with a Mn element or a Co element.